Isabella Kirss

The design of artificial enzymes represents a transformative advancement in biocatalysis, enabling the creation of enzyme for nonnatural reactions. Herein, recent progress in the design of enzymes is highlighted featuring unnatural catalytic residues introduced via site-specific chemical modification. This concept emphasizes the methodologies employed, the challenges, and future directions for expanding potential applications of artificial enzyme design in biocatalysis.

The design of artificial enzymes represents a transformative advancement in biocatalysis, enabling the creation of bespoke biocatalysts for nonnatural reactions. A key innovation in this field is the introduction of unnatural catalytic residues through site-specific chemical modification, which significantly expands the chemical repertoire of natural enzymes. This approach combines precision engineering with cutting-edge methodologies, including chemical ligation, noncanonical amino acid incorporation and directed evolution. These strategies facilitate the development of enzymes with novel catalytic activities, modify substrate specificities, and enhance stability under nonphysiological conditions. This concept examines the methodologies, challenges, and future directions in the design of enzymes with unnatural catalytic residues via site-specific chemical modification, with a focus on their functional impact and transformative potential in synthetic chemistry and biocatalysis.

The noncanonical amino acid, cyanophenylalanine, is genetically inserted close to iron–sulfur clusters of either spinach ferredoxin or iron–iron hydrogenase, and functions as an infrared spectroscopic reporter for changes in cluster redox state.

The noncanonical amino acid, para-cyanophenylalanine (CNF), when incorporated into metalloproteins, functions as an infrared spectroscopic probe for the redox state of iron-sulfur clusters, offering a strategy for determining electron occupancy in the electron transport chains of complex metalloenzymes. A redshift of ≈1–2 cm⁻¹ in the nitrile (NC) stretching frequency is observed, following reduction of spinach ferredoxin modified to contain CNF close to its [2Fe–2S] center, and this shift is reversed on re-oxidation. We extend this to CNF positioned near to the proximal [4Fe–4S] cluster of the [FeFe] hydrogenase from Desulfovibrio desulfuricans. In combination with a distal [4Fe–4S] cluster and the [4Fe–4S] cluster of the active site ‘H-cluster’ ([4Fe–4S]_H), the proximal cluster forms an electron relay connecting the active site to the surface of the protein. Again, a reversible shift in wavenumber for CNF is observed, following cluster reduction in either apo-protein (containing the iron-sulfur clusters but lacking the active site) or holo-protein with intact active site, demonstrating the general applicability of this approach to studying complex metalloenzymes.

Nature Catalysis, Published online: 29 January 2025; doi:10.1038/s41929-025-01290-0

Enzymatic catalysis meets radical coupling

Nature Catalysis, Published online: 26 March 2025; doi:10.1038/s41929-025-01312-x

In the organocatalytic Diels–Alder (DA) reactions, a simple amine is used as a catalyst to form an iminium adduct as an electron-withdrawing group that speeds up reaction with the diene. Now iminium catalysis is identified in Diels–Alderase (DAase) reactions, enabling to substantially broaden the DAase platform.

Nature Catalysis, Published online: 28 March 2025; doi:10.1038/s41929-025-01319-4

Enantioconvergent sp3–sp3 coupling methods are of interest for drug development. Now a visible-light-induced Ni-catalysed ring-opening alkylation of aziridines with olefins is presented to obtain enantioenriched amine-containing sp3–sp3 architectures.

Nature Catalysis, Published online: 18 April 2025; doi:10.1038/s41929-025-01328-3

Supported single atoms are promising catalysts for alkane dehydrogenation, although tuning their reactivity via active site modulation remains a challenge. Here the authors introduce an Ir1–Cu1 dual-atom catalyst for n-butane dehydrogenation that outperforms the corresponding Ir1 single-atom system.

Nature Catalysis, Published online: 18 April 2025; doi:10.1038/s41929-025-01325-6

Engineered polyketide synthases (PKSs) have great potential as biocatalysts for the synthesis of chemically challenging molecules. Here the authors show a retrobiosynthesis approach to design and construct PKSs to produce a series of valerolactams for biopolymer production.

Nature Catalysis, Published online: 29 April 2025; doi:10.1038/s41929-025-01329-2

Enantiocontrolled transformation of carbenium ions is challenging due to their instability and high reactivity. Now, combining a chiral organocatalyst with a photocatalyst enables enantioselective intramolecular amidation of C(sp3)–H bonds to afford chiral oxazolidine products via a transient carbenium ion complex.